An international mobile subscriber identity (IMSI) is a unique number associated with user equipment (for example, a cellular phone) of cellular subscribers of a cellular network, such as one of a global system for mobile communications (GSM) network, a universal mobile telecommunications system (UMTS) network, a long-term evolution (LTE) network, and a CDMA2000 network. The IMSI can be stored either directly within the user equipment or within a subscriber identity module (SIM) card of the user equipment. The IMSI includes: an identifier that identifies a network operator to identify the cellular network provider with whom a subscriber has an account, and an identifier that uniquely identifies the user equipment or the SIM card and, thus, the subscriber registered as owner of the user equipment or the SIM card, respectively.
In a LTE network, messages, including the IMSI, are passed between a user equipment (UE) and a mobile management entity (MME) via a non-access stratum (NAS) functional layer of the LTE protocol stack. A base station (for example, an evolved Node B (eNodeB)) of the LTE network traditionally does not have the capability of deciphering NAS messages. The base station accordingly does not have access to the IMSI, and might, therefore, not match subscribers with respective communication data. Such matching of subscribers with corresponding communication data can be useful to perform many communication network functions, such as, for example, generating a financial charge of each subscriber based on usage of cellular data by each user, identifying subscribers and providing data to third party servers, etc., and the like. The base station, however, has the quickest and maximum access to most communication data, other than the IMSI, associated with a user. Therefore, there is a need to make IMSI available at the base station, as such availability can enable performance of the above-referred communication functions in a fast and accurate manner.